[ion] Provision to clock the CPU at 96 MHz

Change-Id: I397ff23941dfff3ea3c2e217c0fb1ba242326cfb

ion/src/device/device.cpp

@@ -35,6 +35,36 @@ void Ion::Device::init() {
 }
 
 void Ion::Device::initClocks() {
+#define USE_96MHZ_SYSTEM_CLOCK 0
+#if USE_96MHZ_SYSTEM_CLOCK
+  /* System clock
+   * Configure the CPU at 96 MHz, APB2 and USB at 48 MHz. */
+
+  /* After reset the Flash runs as fast as the CPU. When we clock the CPU faster
+   * the flash memory cannot follow and therefore flash memory accesses need to
+   * wait a little bit.
+   * The spec tells us that at 2.8V and over 90MHz the flash expects 3 WS. */
+  FLASH.ACR()->setLATENCY(3);
+
+  /* We're using the high-speed internal oscillator as a clock source. It runs
+   * at a fixed 16 MHz frequency, but by piping it through the PLL we can derive
+   * faster oscillations. Combining default values and a PLLQ of 4 can provide
+   * us with a 96 MHz frequency for SYSCLK. */
+  RCC.PLLCFGR()->setPLLQ(4);
+  RCC.PLLCFGR()->setPLLSRC(RCC::PLLCFGR::PLLSRC::HSI);
+  // 96 MHz is too fast for APB1. Divide it by two to reach 48 MHz
+  RCC.CFGR()->setPPRE1(RCC::CFGR::AHBRatio::DivideBy2);
+
+  // Enable the PLL and wait for it to be ready
+  RCC.CR()->setPLLON(true);
+  while(!RCC.CR()->getPLLRDY()) {
+  }
+
+  // Last but not least, use the PLL output as a SYSCLK source
+  RCC.CFGR()->setSW(RCC::CFGR::SW::PLL);
+  while (RCC.CFGR()->getSWS() != RCC::CFGR::SW::PLL) {
+  }
+#endif
 
   // Peripheral clocks
 

ion/src/device/regs/flash.h

@@ -0,0 +1,23 @@
+#ifndef REGS_FLASH_H
+#define REGS_FLASH_H
+
+#include "register.h"
+
+class FLASH {
+public:
+  class ACR : public Register32 {
+  public:
+    REGS_FIELD(LATENCY, uint8_t, 3, 0);
+  };
+
+  constexpr FLASH() {};
+  REGS_REGISTER_AT(ACR, 0x00);
+private:
+  constexpr uint32_t Base() const {
+    return 0x40023C00;
+  }
+};
+
+constexpr FLASH FLASH;
+
+#endif

ion/src/device/regs/rcc.h

@@ -5,6 +5,45 @@
 
 class RCC {
 public:
+  class CR : public Register32 {
+  public:
+    REGS_BOOL_FIELD(PLLRDY, 25);
+    REGS_BOOL_FIELD(PLLON, 24);
+  };
+
+  class PLLCFGR : public Register32 {
+  public:
+    REGS_FIELD(PLLM, uint8_t, 5, 0);
+    REGS_FIELD(PLLN, uint16_t, 14, 6);
+    REGS_FIELD(PLLP, uint8_t, 17, 16);
+    enum class PLLSRC {
+      HSI = 0,
+      HSE = 1
+    };
+    void setPLLSRC(PLLSRC s) volatile { setBitRange(22, 22, (uint8_t)s); }
+    REGS_FIELD(PLLQ, uint8_t, 27, 24);
+    REGS_FIELD(PLLR, uint8_t, 30, 28);
+  };
+
+  class CFGR : public Register32 {
+  public:
+    enum class SW {
+      HSI = 0,
+      HSE = 1,
+      PLL = 2
+    };
+    void setSW(SW s) volatile { setBitRange(1, 0, (uint8_t)s); }
+    SW getSWS() volatile { return (SW)getBitRange(3,2); }
+    enum class AHBRatio {
+      One = 0,
+      DivideBy2 = 4,
+      DivideBy4 = 5,
+      DivideBy8 = 6,
+      DivideBy16 = 7
+    };
+    void setPPRE1(AHBRatio r) volatile { setBitRange(12, 10, (uint32_t)r); }
+  };
+
   class AHB1ENR : public Register32 {
   public:
     AHB1ENR(uint32_t v) : Register32(v) {}
@@ -40,6 +79,9 @@ public:
   };
 
   constexpr RCC() {};
+  REGS_REGISTER_AT(CR, 0x00);
+  REGS_REGISTER_AT(PLLCFGR, 0x04);
+  REGS_REGISTER_AT(CFGR, 0x08);
   REGS_REGISTER_AT(AHB1ENR, 0x30);
   REGS_REGISTER_AT(AHB3ENR, 0x38);
   REGS_REGISTER_AT(APB1ENR, 0x40);

ion/src/device/regs/regs.h

@@ -5,6 +5,7 @@
 #include "exti.h"
 #include "cm4.h"
 #include "fsmc.h"
+#include "flash.h"
 #include "rcc.h"
 #include "gpio.h"
 #include "syscfg.h"